The rotor of the turbofan of an engine fitted to civil aircraft comprises a disk driven by the low-pressure shaft and on the periphery of which are held a plurality of blades extending radially by their end forming the root. According to a normal structure, the root of the blades has a dovetail section and the latter are housed in recesses machined into the rim of the disk in a substantially axial direction. Immediately downstream of the fan disk and forming the same rotor is the supercharging compressor. The latter is in the form of a drum and comprises several stages of blades.